The spe-11 gene encodes a sperm-supplied product required for normal embryogenesis in the nematode Caenorhabditis elegans. The mutant phenotype is patemal-effect embryonic lethality: wild-type oocytes fertilized by sperm from mutant animals undergo abnormal early development and arrest as multinucleate, one-celled embryos. The multiple and pleiotropic defects observed in these arrested embryos suggest the phenotype may be caused by incomplete fertilization of the oocyte. We are interested in determining which aspects of fertilization may be defective in the mutant embryos. One phenomenon consistently observed in other species is a transient increase in the level of free calcium in the oocyte shortly after sperm entry. We would like to detemline whether this type of calcium "spike" occurs during fertilization in C elegans, and if so, determine if spe-11 mutant embryos are altered in this response. The absence of methods to in vitro fertilize oocytes in C. elegans necessitates perfomling these experiments in vivo. The two-photon technology offers us the opportunity to observe calcium fluctuations during the oocyte's natural fertilization process inside the animal. We want to work with the IMR to obtain time-lapse images of these calcium fluctuations in oocytes injected with fluorescent calcium indicator dyes.